1. Field of the invention
The present invention relates to an apparatus for automatically adjusting yoke clearance in a steering device, and more particularly to an apparatus for automatically adjusting yoke clearance in a steering device, which includes a middle member for removing a clearance between a yoke plug and a support yoke and applying force in a direction of a rack bar to the yoke plug, so as to automatically compensate for a clearance caused by long time use of the steering device.
2. Description of the Prior Art
A steering device refers to an apparatus for changing a proceeding direction of a vehicle according to a driver's will, which can help the driver to freely change the direction in which a front wheel of the vehicle turns around, so as to move the vehicle in the direction the driver wants.
FIG. 1 is a view schematically showing a steering device for a common vehicle.
As shown in FIG. 1, a conventional steering device includes a steering wheel 100 placed at a driver's seat and a steering shaft 105 connected thereto, a steering column 103 fixing the steering shaft to a vehicle body, a gear box 130 including a rack gear 110 and a pinion gear 120, which convert a rotation force received from the steering shaft 105 into a rectilinear motion, a rack bar 140 including inner ball joints 135 at both ends thereof, a tie rod 150 integrally formed with a ball of the inner ball joint 135, and an outer ball joint 155 disposed at the end of the tie rod 150.
In the case of a Rack and Pinion Gear type steering device, inner ball joints 135 are disposed at right and left ends of the rack bar 140 on which the rack gear 110 is formed. The inner ball joints 135 are connected to the tie rods 150. Additionally, the tie rod 150 is connected to the outer ball joint 155 and transmits force to a knuckle 159 to steer tires 158.
FIG. 2 is a view showing a cross-section of a conventional gear box.
The conventional Rack and Pinion type gear box 130 includes a pinion gear 120, a rack bar 140, a support yoke 260, a spring 263 and a yoke plug 265. The Rack and Pinion type gear box 130 converts the rotation force received from a steering shaft (not shown) into a rectilinear motion, as described above.
The rack bar 140 is engaged with the pinion gear 120, and converts the rotational motion into a rectilinear motion. An apparatus for supporting the rack bar 140 in the direction of the pinion gear 120 so as to help engagement between the rack bar 140 and the pinion gear 120 is disposed on the rear surface of the rack bar 140.
The apparatus for supporting the rack bar 140 includes the support yoke 260, the spring 263 and the yoke plug 265. The support yoke 260 is disposed on the opposite side to the rear surface of the rack bar 140, that is, on the opposite side to the surface on which the rack gear 110 is formed. The support yoke 260 is inserted in the cylinder 250 of the gear box 130 and is linearly movable in a direction perpendicular to the rack bar 140.
The support yoke 260 has a cylindrical shape so that it can linearly slide within the cylinder 250. A front part of the support yoke 260 is in contact with the rack bar 140 and has a semicircular groove that can come in close contact with the rear surface of the rack bar 140.
In addition, the spring 263 is disposed behind the support yoke 260 so as to push the support yoke 260 with a constant pressure and compensate for a clearance between the rack bar 140 and the pinion gear 120, so that the rack bar 140 and the pinion gear 120 can come into close contact with each other and can effectively transfer force between them.
Such a support yoke 260 causes friction while sliding on the rear surface of the rack bar 140. A plastic support yoke 260 which is more ductile than the rack bar 140 is usually used in order to prevent the rack bar 140 from being worn or from generating noise due to the sliding friction.
The spring 263 performs a function of applying pressure to the support yoke 260 to come in close contact with the rack bar 140, and a coil spring is generally used as the spring 263 above. The yoke plug 265 is disposed at the rear surface of the spring 263 and support the spring 263.
The yoke plug 265 applies pressure to the support yoke 260 by supporting the spring 263. A male screw thread is commonly formed on the yoke plug 265 so that the yoke plug 265 is engaged with a female screw thread formed on the gear box 130. A groove into which a wrench can be inserted is formed on the rear surface of the yoke plug 260.
As such, since a conventional assembling structure of the support yoke 260 employs a screw coupling method, the conventional assembling structure has a very weak assembling ability and requires an additional process of adjusting and examining a yoke clearance after the assembling. Moreover, the conventional assembling structure has a clearance (see A of FIG. 2, hereinafter, referred to as ‘yoke clearance’) formed between the support yoke 260 and the yoke plug 265, and has rattle noise generated due to contact between the support yoke 206 and the yoke plug 265 when the rack bar 140 strongly pushes the support yoke 260 in a reverse direction by a force reversely input from the irregular road surface, etc.